A logo of Alibaba Group is pictured at its headquarters in Hangzhou, Zhejiang province, China, October 14, 2015. REUTERS/Stringer

SHANGHAI (Reuters) - A Chinese regulator has formally accepted a request by JD.com, the country’s second-biggest online retailer, to investigate its rival Alibaba Group Holding Ltd for possible unfair practices during promotions, JD.com’s official microblog said on Thursday.

Alibaba, China’s biggest e-commerce firm, has previously denied accusations outlined in a JD.com letter to the State Administration for Industry and Commerce (SAIC) in the run-up to Nov. 11 ‘Singles’ Day’ promotions, the biggest online shopping day of the year in China.

JD.com said in its letter said Alibaba, was “forcing merchants” to choose to deal exclusively with one e-commerce site for promotional activities. The two companies have a long-standing rivalry, with little love lost between their founders.

An SAIC official in Beijing said by telephone he had no information about the case.

An Alibaba spokesman declined to comment.

JD.com’s complaint refers to an SAIC regulation that forbids e-commerce platforms from limiting or barring their merchants from participating in promotions on other platforms. The regulation came into effect on Oct. 1.

“We are ready to actively cooperate with national administrative organs to regulate order in the e-commerce industry, and spare no effort and persevere to the end in order to protect the legitimate rights and interests of businesses and consumers,” JD.com said.